1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, to a plasma display panel capable of improving the contrast using a black matrix.
2. Description of the Related Art
In general, a plasma display panel (hereafter, referred to as PDP) is a display device that uses the visible rays generated when vacuum ultraviolet rays generated by gas discharge excite phosphor.
The PDP is thinner in thickness and lighter in weight than the cathode ray tubes (CRTs) that have been usually employed as display devices. The PDP has an advantage in that a high definition and large-sized screen can be realized.
The PDP that has such advantages described above includes many discharge cells arranged in matrix fashion and each of the discharge cells works as one pixel of a screen.
FIG. 1 illustrates the structure of three-electrode AC surface discharge type PDP in the related art. Even though FIG. 1 depicts one discharge cell 1 for the convenience of explanation, a PDP has generally many millions of the discharge cells 1 shown in the FIG. 1 in matrix fashion.
Referring to FIG. 1, a three-electrode AC surface discharge type PDP in the related art includes first electrodes 12Y and second electrodes 12Z formed on a front substrate 10 and address electrodes 20X formed on a rear substrate 18.
A front dielectric layer 14 and a protective layer 16 are laminated on the front substrate 10 that has the first electrodes 12Y and the second electrodes 12Z arranged in parallel. Wall charge generated during plasma discharge is stored on the front dielectric layer 14. The front dielectric layer 14 is designed to have a thickness within 30 xcexcm to 45 xcexcm. The protective layer 16 protects the front dielectric layer 14 from damages caused by sputtering during plasma discharge and also improves the second electrons emission efficiency. The protective layer 16 is usually made of magnesium oxide (MgO).
A rear dielectric layer 22 and barrier ribs 24 are formed on the rear substrate 18 that has the address electrodes 20X formed thereon. A phosphor layer 26 is coated on the surfaces of the rear dielectric layer 22 and the barrier ribs 24. The address electrodes 20X is formed in the direction to cross over the first electrodes 12Y and the second electrodes 12Z. The barrier ribs 24 are formed in parallel with the address electrodes 20X so as to prevent the ultraviolet rays and the visible rays generated by the plasma discharge from leaking into the neighboring discharge cells 1.
The phosphor layer 26 is excited by the ultraviolet rays generated during the plasma discharge so as to generate one of visible rays of red, green and blue colors. The inert gas for discharge is injected into discharge spaces prepared between the front substrate 10/the rear substrate 18 and the barrier ribs 24. As shown in FIG. 2, a black matrix is formed between the first electrode 12Y and the second electrode 12Z which are respectively formed in the neighboring discharge cells 1. FIG. 2 illustrates the front substrate 10 of PDP shown in FIG. 1. As shown in FIG. 2, a black matrix 30 is formed between a first electrodes group including the electrodes 12Y1 and the second electrodes 12Z1 and a second electrodes group including the electrodes 12Y2 and the second electrodes 12Z2 that are different from electrodes 12Y1 and the second electrodes 12Z1 respectively. More particularly, the black matrix 30 is formed on the areas from the external edge 11 of the second electrodes 12Z1 included in the first electrodes group to the external edge 13 of the first electrodes 12Y2 included in the second electrodes group.
In this AC surface discharge type PDP, one frame is divided into a few subfields each of which is different from others in the number of discharge times so as to display the gray levels of images. Each of the subfields is divided into a reset period for generating a uniform discharge, an address period for selecting a discharge cell, and a sustain period for displaying gray levels according to the number of discharge times. For example, to display an image in 256 gray levels, the frame period (16.67 ms) corresponding to one 60th second is divided into eight subfields.
Each of the eight subfields is divided into the reset period, the address period and a sustain period. The reset period of each subfield is the same as the address period in length while the sustain period increases at each subfield at the ratio of 2n (n=0, 1, 2, 3, 4, 5, 6 and 7). In this way, the sustain period of each field is different from that of other fields, and hence the gray levels of the image can be displayed.
In the reset period, reset pulses are applied to the first electrodes 12Y to cause reset discharge. In the address period, scan pulses are applied to the first electrodes 12Y and data pulses are applied to the address electrodes 20X to cause address discharge between two electrodes 12Y and 20X. The wall charge is created on the front dielectric layer 14 and the rear dielectric layer 22 during the address discharge. In the sustain period, AC signals that are alternatively applied to the first electrodes 12Y and the second electrodes 12Z cause sustain discharge between two electrodes 12Y and 12Z.
In such a PDP of the related art, the contrast is degenerated due to the reset discharge caused in the reset period and the address discharge caused in the address discharge. In other words, the light generated by the reset discharge and the address discharge lowers darkroom contrast since the reset discharge and the address discharge do not contribute to the brightness of the PDP.
In order to improve the contrast, as shown in FIG. 3, a black matrix 32 is formed on the areas from the external edge 15 of the second electrodes 12Z1 included in the first electrodes group to the external edge 17 of the first electrodes 12Y2 included in the second electrodes group. The black matrix 32 shields the light generated by the reset discharge and the address discharge to improve the contrast. Since the light generated by the first electrodes 12Y2 during the reset discharge and the address discharge does not contribute to the brightness, the black matrix 32 shields the light to improve the contrast.
However, the black matrix 32 to improve the contrast also shields the light generated by the sustain discharge that contributes to the brightness. The sustain pulses are applied to the first electrodes 12Y2. It is desired that the light generated by the sustain discharge should not be shielded since it contributes to the brightness. In case a black matrix 32 is formed on the areas from the external edge 15 of the second electrodes 12Z1 included in the first electrodes group to the external edge 17 of the first electrodes 12Y2 included in the second electrodes group, the black matrix 32 also shields the light generated by the sustain discharge so that the brightness degenerates and also the light emission efficiency and the display quality deteriorate.
An object of the invention is to at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
Accordingly, it is an object of the present invention to provide a plasma display panel capable of enhancing the contrast by overlapping a first electrode to which scan pulses are applied among a plurality of electrodes with a black matrix.
These and other objects and advantages of the invention are achieved by providing a plasma display panel which includes: a first electrodes group including a first electrode formed on a front substrate, a second electrode formed in parallel with and near to the first electrode, and a third electrode formed in parallel with and spaced widely from the second electrode; a second electrodes group formed adjacent to the first electrodes group, and including first to third electrodes, the first to third electrodes of the second electrodes group playing the same roles as the first to third electrodes of the first electrodes group; and a plurality of black matrices formed between the neighboring first electrodes group and the neighboring second electrodes group to be overlapped with the first electrodes of the first electrodes group and the first electrodes of the second electrodes group.
Preferably, the first to the third electrodes of the second electrodes group are formed in a same order as the first to third electrodes of the first electrodes group, and the black matrices are overlapped between the neighboring first electrodes group and the neighboring second electrodes group.
Preferably, the first electrodes, the second electrodes and the third electrodes of the second electrodes group are arranged symmetrically to the first electrodes, the second electrodes and the third electrodes of the first electrodes group.
Preferably, the plasma display panel further includes: a front dielectric layer formed to cover the first electrodes group, the second electrodes group and the front substrate; and a protective layer formed to cover the front dielectric layer.
Preferably, the black matrices are formed between the front dielectric layer and protective layer.
According to another aspect of the present invention, a plasma display panel includes: a first electrodes group including a first electrode formed on a front substrate, a second electrode formed in parallel with and near to the first electrode, and a third electrode formed in parallel with and spaced widely from the second electrode; a second electrodes group provided with a first electrode, a second electrode and a third electrode formed in a same order as and adjacent to the first to third electrodes of the first electrodes group, the first to third electrodes of the second electrodes group playing same roles as the first to third electrodes of the first electrodes group; a plurality of black matrices formed between the neighboring first electrodes group and the neighboring second electrodes group to be overlapped with areas from external edges of the third electrodes of the first electrodes group to the first electrodes of the second electrodes group; a front dielectric layer formed to cover the first electrodes group, the second electrodes group and the front substrate; and a protective layer formed to cover the front dielectric layer.
According to further another aspect of the present invention, a plasma display panel includes: a first electrodes group including a first electrode formed on a front substrate, a second electrode formed near to the first electrode, and a third electrode formed spaced widely from the second electrode; a second electrodes group including first to third electrodes, the first to third electrodes of the second electrodes group being formed symmetrically to the first to third electrodes of the first electrodes group with respect to left and right directions and playing the same roles as the first to third electrodes of the first electrodes group; a plurality of black matrices formed between the neighboring first electrodes group and the neighboring second electrodes group to be overlapped with the first electrodes of the first electrodes group and the first electrodes of the second electrodes group; a front dielectric layer formed to cover the first electrodes group, the second electrodes group and the front substrate; and a protective layer formed to cover the front dielectric layer.
According to still another aspect of the present invention, a plasma display panel includes: a first dielectric layer formed on a front substrate; a first electrodes group including a first electrode formed on the first dielectric layer, a second electrode formed in parallel with and near to the first electrode, and a third electrode formed in parallel with and spaced widely from the second electrode; a second electrodes group including first to third electrodes formed adjacent to the first to third electrodes of the first electrodes group, the first to third electrodes of the second electrodes group playing the same roles as the first to third electrodes of the first electrodes group; a second dielectric layer formed to cover the first electrodes group and the second electrodes group; a protective layer formed to cover the second dielectric layer; and a plurality of black matrices formed between the front substrate and the first dielectric layer and between the neighboring first electrodes group and the neighboring second electrodes group to be overlapped with the first electrodes of the first electrodes group and the first electrodes of the second electrodes group.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.